Development of performance measures for dynamic parameter design problems

The objective of the Taguchi parameter design is to improve the performance of a product or a process by determining the levels of its design parameters such that the performance characteristic is robust against various causes of variation. Parameter design problems are broadly classified into static and dynamic ones. Static problems are further classified into the-nominal-thebest, the-larger-the-better and the-smaller-the-better ones, and for each problem type a unique performance measure (or an SN ratio) is appropriately defined. However, for the dynamic parameter design problem, such a classification has not been explicitly made. The only case that has been extensively discussed in the literature is the one where the slope β of the relationship between the performance characteristic and the signal parameter has a finite ideal value. In this article, we consider the cases in which it is desired to have β as large as and as small as possible, and develop a performance measure for each case. In addition, the existing performance measure for the case where β has a finite ideal value is modified according to the framework proposed in this article. The developed parameter design procedures are illustrated with an example.